1. Field of the invention
This invention relates to 4,5-dihydro-4,5-dioxo-1H-1-benzopyrano[2,3-b]pyridine-3-carboxylic acids, their esters and the non-toxic pharmaceutically acceptable salts thereof, which are active in the prevention of allergic and asthmatic reactions in mammals.
2. Description of the Prior Art
United States application Ser. No. 736,788, filed Oct. 29, 1976 now U.S. Pat. No. 4,046,769 and United States application Ser. No. 736,926, filed Oct. 29, 1976, now U.S. Pat. No. 4,066,655 disclose structurally distinct benzopyrancarboxylic acids which also demonstrate anti-allergic and anti-asthmatic activity. Specifically, United States application Ser. No. 736,788 describes 4,10-dihydro-4,10-dioxo-1H-1-benzopyrano (3,2-b) pyridine-2-carboxylic acids; and United States application Ser. No. 736,926 describes 4,10-dihydro-4,10-dioxo-1H-1-benzopyrano(3,2-b)pyridine-3-carboxylic acids.